Alopecia

BASICS

DEFINITION

Alopecia is common in chinchillas and is characterized by complete or partial lack of hair in expected areas. It may be multifactorial and can be either a primary or secondary disorder. As many as 60 hairs grow from a single hair follicle in a healthy chinchilla.

PATHOPHYSIOLOGY

• Multifactorial causes
• Disruption in the growth of hair follicles is possible with infection, inflammation, trauma, or blockage of the receptor sites for stimulation of the cycle.

SYSTEMS AFFECTED

• Skin/exocrine
• Behavioral-may cause self-inflicted chewing, biting
• Gastrointestinal-especially dental disease; may cause anorexia, dysphagia, ptyalism
• Hemic/lymphatic/immune
• Ophthalmic-ophthalmic or dental disease may cause epiphora and conjunctivitis resulting in alopecia surrounding one or both eyes.

GENETICS

• Dental disease-avoid breeding affected animals as inheritance of dental disease is suspected.
• Fur chewing-avoid breeding animals that chew fur.

INCIDENCE/PREVALENCE

Common condition in chinchillas

GEOGRAPHIC DISTRIBUTION

N/A

SIGNALMENT

No specific age or sex predilection

SIGNS

• The pattern and degree of hair loss are important for establishing a differential diagnosis.
• Multifocal patches of alopecia-most frequently associated with folliculitis from mycotic or bacterial infection
• Large, diffuse areas of alopecia-indicate follicular dysplasia or metabolic component; not reported in chinchillas but should be considered
• May be acute or slowly progressive in onset

Historical Findings

• Inappropriate diet-fiber deficiency, other nutritional deficiencies
• Inappropriate frequency or complete lack of dust bath; use of inappropriate dust bath materials
• Inappropriate sanitation, ventilation
• Self-inflicted or conspecific barbering
• Drooling, dysphagia
• Ocular or nasal discharge
• History of fur slip, fur chewing

Physical Examination Findings

• Alopecia with or without scaling, crusting-distribution may help differentiate the disease process.
• Broken hair shafts-suggestive of barbering (self-inflicted or conspecific)
• Ptyalism-associated with dental malocclusion; a thorough oral examination is critical for evaluating for premolar/molar malocclusion
• Epiphora-associated with dental malocclusion; a thorough oral examination is critical for evaluating for premolar/molar malocclusion

CAUSES

• Normal shedding pattern-some chinchillas may lose hair in patches when shedding
• Behavioral-barbering; dominant chinchillas may chew or pull out hair of submissive cagemates
• Parasitic-ectoparasites (fleas, lice, and mites)-uncommon in chinchillas because of their dense coat
• Infectious-dermatophytosis, bacterial pyoderma; most often a secondary problem, especially moist dermatitis (e.g., ptyalism, epiphora, and urine scald)
• Trauma-fur slip due to excessive restraint; self- or conspecific-inflicted barbering, bite wounds
• Neoplastic-cutaneous lymphoma, trichofolliculoma, mast cell tumor
• Nutritional-especially protein and fiber deficiencies

RISK FACTORS

Poor husbandry: lack of dust baths, proper ventilation, and sanitation; nutritional deficiencies such as low-fiber diets leading to fur chewing and other deficiencies allowing for immunosuppression; traumatic handling leading to fur slip.

DIAGNOSIS

DIFFERENTIAL DIAGNOSIS

Differentiating Causes

Pattern and degree are important for differential diagnoses.

Symmetrical Alopecia

• Barbering-broken fur shafts identified on close inspection; most commonly on dorsal flanks, around face and ears; can have a "moth-eaten" appearance to the coat. Owners may or may not observe barbering between animals.
• Fur chewing-very common in chinchillas; may chew on fur constantly or intermittently and fur may regrow in between episodes. Usually chew dorsal flanks and sides, pregnant females may chew temporarily. Coat may have moth-eaten appearance.
• Matted fur associated with high environmental temperature (>80°F/26.7°C), humid environment, or if dust baths are inadequate or not provided.

Multifocal to Focal Alopecia

• Lack of proper dust bath-may cause poor, unkempt coat that becomes matted and sheds abnormally; may cause alopecia and accumulation of scale in matted areas
• Trauma
  • Bite wounds-alopecia, with or without erythema; can abscess; secondary Staphylococcus spp. or Streptococcus spp. infections may occur
  • Fur slip-alopecia, with or without erythema, no scaling
  • Ear trauma, including frost-bite alopecia with erythema, scaling, necrosis of pinnae
• Fur chewing-may chew on fur constantly or intermittently and fur may regrow in between episodes; usually chew dorsal flanks and sides, pregnant females may chew temporarily
• Dental disease-facial moist dermatitis associated most commonly with ptyalism or epiphora; alopecia, with or without erythema, scale, or ulceration; Staphylococcus spp. or Streptococcus spp. infections can occur secondary to moist dermatitis.
• Dermatophytosis-Trichophyton mentagrophytes are most common, but Microsporum canis and M. gypseum have been identified; partial or complete alopecia with scaling and pruritis; with or without erythema, not always ring-shaped; may begin as alopecia around eyes, nose, then spread to feet, body, genitals. May be first identified on the "grooming claw" (medial first digit) of hind limbs.
• Cheyletiella spp.-reported in chinchillas, lesions are usually located in the intrascapular or tail-base region and are associated with large amounts of white scale. Mites are readily identified on skin scrapes or acetate tape preparations on low power.
• Urinary tract infection-perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Arthritis of hind limbs-perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Lumbar spinal spondylosis-perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Pododermatitis of hind limbs-perineal moist dermatitis; alopecia, with or without erythema, scale, or ulceration
• Abscesses-anywhere on body; alopecia, with or without erythema, scale, ulceration
• Ear mites-alopecia around base of ear; may extend to head, neck, abdomen, perineal region, intense pruritis; brown-beige crusty exudate in ear canal and pinna
• Fleas-patchy alopecia; flea dirt will help differentiate; secondary pyoderma sometimes seen
• Contact dermatitis-alopecia, with or without erythema; scale on ventral abdomen and other contact areas
• Moist dermatitis-alopecia, with or without erythema, scale, or ulceration associated with urinary disease (urine scald), diarrhea, uneaten cecotropes, arthritis, pododermatitis, spinal spondylosis
• Neoplasia-cutaneous lymphoma, cutaneous epitheliotropic lymphoma (mycosis fungoides), trichofolliculoma, mast cell tumors; focal or diffuse alopecia; scaling and erythema; may see crust formation-not reported in chinchillas but should be considered.

CBC/BIOCHEMISTRY/URINALYSIS

To identify evidence of infection, inflammation, and organ function for underlying disease, especially with urine scald, perineal dermatitis, infectious organisms

OTHER LABORATORY TESTS

Fungal cultures-especially DTM for dermatophytes; two negative cultures should be obtained following treatment to ensure clearance of infection.

IMAGING

• Skull radiographs-to identify underlying dental disease in chinchillas with ptyalism, epiphora
• Whole body radiographs-to identify orthopedic, spinal, gastrointestinal, renal, reproductive diseases associated with perineal dermatitis or urine scald
• Abdominal ultrasound-to identify gastrointestinal, renal, reproductive diseases associated with perineal dermatitis or urine scald

DIAGNOSTIC PROCEDURES

• Skin scraping-micro-spatula with flat-ended blade (preferable) or dull edge of scalpel blade
• Acetate tape preparation-evaluate on low-power microscopy for ectoparasites
• Trichogram-cytology of epilated hairs to examine for lice, other ectoparasites, or eggs
• Skin biopsy-especially with suspicion of neoplasia, infectious organisms
• Woods lamp ultraviolet evaluation of Microsporum canis lesions; not very useful as a screening tool-many pathogenic dermatophytes, including T. mentagrophytes, do not fluoresce; false fluorescence is also common.
• Fungal culture-if dermatophytes are...